Currently, a widely used form of shaving preparation is the type referred to as a post-foaming shave gel. These post-foaming shave gels are now well-known and have been described, for example, in U.S. Pat. No. 2,995,521 (Bluard), U.S. Pat. No. 3,541,581 (Monson), U.S. Pat. No. 4,405,489 (Sisbarro), U.S. Pat. No. 4,528,111 (Su), U.S. Pat. No. 4,651,503 (Anderson), U.S. Pat. No. 5,248,495 (Patterson), U.S. Pat. No. 5,308,643 (Osipow), U.S. Pat. No. 5,326,556 (Bamet), U.S. Pat. No. 5,500,211 (George), U.S. Pat. No. 5,560,859 (Hartmann), U.S. Pat. No. 5,858,343 (Szymczak) and WO 02/47636 (Lasota). Such compositions generally take the form of an oil-in-water emulsion in which the post-foaming agent, generally a volatile (i.e., low boiling point) aliphatic hydrocarbon, is solubilized in the oil phase, and the water phase comprises a water-dispersible soap or interrupted soap component. The product is generally packaged in an aerosol container with a barrier, such as a piston or collapsible bag, to separate the post-foaming gel from the propellant required for expulsion of the product. The product is dispensed as a clear, translucent or opaque gel that is substantially free from foaming until it is spread over the skin, at which time it produces a foam lather generated by the volatilization of the volatile hydrocarbon foaming agent.
Users of wet-shave razors generally appreciate a feeling of warmth against their skin during shaving. The warmth feels good, and also causes the user's skin to hydrate and beard to soften, resulting in a more comfortable shave.
Various attempts have been made to provide a warm feeling during shaving. For example, shaving foams have been formulated to react exothermically upon release from the shaving canister, so that the foam imparts warmth to the skin, e.g., as described in U.S. Pat. Nos. 3,341,418, 3,772,203, 3,819,524, 3,866,800, and U.S. Pat. No. 3,878,118. However, up to now no self-heating shaving gels have been commercialized even though shaving gels are highly preferred over shaving foams. Thus, it would be highly desirable to provide a post-foaming shave gel product that is self-heating.